This invention relates to a process for the production of polyether polyols based on triazole-group containing hydroxy materials and the novel polyether polyols produced by this process. The present invention also relates to isocyanate-reactive compositions comprising these polyether polyols, and to a process for the production of a polyurethane comprising reacting a polyol and a polyisocyanate wherein the polyol comprises the polyether polyols of the present invention.
Polyether polyols are known in the art for the preparation of polyurethane foams. The polyether polyols are prepared by reacting a polyhydric alcohol such as sucrose, diethylene glycol, trimethylolpropane, etc., with an alkylene oxide such as, for example, ethylene oxide or propylene oxide, in the presence of an alkaline catalyst such as sodium hydroxide. After reaction, the alkaline catalyst is typically removed by one of various methods. Suitable processes for the production of polyether polyols and removal of catalyst residues as are described in, for example, U.S. Pat. Nos. 3,000,963, 3,299,151, 4,110,268, 4,380,502 and 4,430,490.
It is known that the physical and mechanical characteristics of foamed polyurethanes depend, at least to a certain degree, upon the structure and molecular size of the polyethers which are used to produce them.
Amine-initiated polyether polyols and processes for their production are known and described in, for example, U.S. Pat. Nos. 4,877,879 and 5,786,405, and Japanese Abstracts 57168917A and 57168918. These polyether polyols show promising results in foam-forming systems blown without CFC blowing agents. Such polyether polyols can be formed by reacting an amine such as, for example, toluene diamine, with an alkylene oxide such as, for example, ethylene oxide or propylene oxide. This reaction may also be catalyzed with an alkaline catalyst such as potassium hydroxide. The addition of conventional antioxidants such as, for example, butylated hydroxyl toluene (BHT) to the resultant amine-initiated polyether polyols is preferred to minimize color formation in the polyether polyols and foams produced therefrom.
Substantially linear, thermoplastic aromatic polyethers which contain azo groups in the backbone are also known, as disclosed in U.S. Pat. No. 5,064,929. Unlike the above mentioned polyether polyols, however, these thermoplastic polyethers are not precursors in polyurethane reactions. They are instead finished polymers. In addition, they are not hydroxyl-terminated and thus, are incapable of reacting with polyisocyanates. The presence of the internal azo moiety also results in highly colored polymers which would obviously be unsuitable for applications where low color is desirable.
As is commonly known, the reaction of polyols and isocyanates can lead to discolored foam due to chemical or thermal oxidation. This is minimized by the addition to polyether polyols of common antioxidants such as, for example, butylated hydroxy toluene (BHT). In recent years, however, concerns have arisen about the use of low molecular weight antioxidants in PU formulations; concerns relative to the migration of these antioxidants to the surface of the foam, thereby creating exposure problems. The advantage of the present invention is that the antioxidant is chemically bound to the polyether polyol, thereby eliminating the potential for exposure due to the migration of these antioxidants.